Atari 9 Pin Circuit

Depending on the controller being used there may or may not be any need for additional electronics.

The simplest case would be where the control pad buttons are activated by being pulled to ground. In this case no extra electronics would be needed. Instead the control pad button contacts would be directly wired to the Atari joystick lines. This was the situation for my 2nd Atari 9 Pin Interface.

However the Joytech pad I used for my original Atari 9 Pin Interface was more complicated. Instead of each control pad button having its own line - they were wired in pairs. One button would pull the control line up high to 3v6 and the opposite button would pull the line low to ground. Therefore a simple circuit was required:

Input 1	Input 2	Output 1
Disconnected	Disconnected	Disconnected
Disconnected	Low	Low
Low	Disconnected	High
Low	Low	N/A

As the inputs are connected to opposite joystick directions - they should never be both Low together. If they were then the 3v6 and Ground lines would become shorted out which would probably blow the transistors - or worse still the fuse inside the Playstation. I probably should add a current limiting resistor to the circuit.

One of these circuits is required for UP/DOWN - and another identical one is required for LEFT/RIGHT. Fortunately there are enough gates on the 4049 chip to do both. Additionally though 4 transistors and 8 resistors are needed for the complete circuit. I also added a .1uF decoupling capacitor across the 4049’s power lines - ending up with a very crowded circuit board!

The values of the resistors are not very important (though 1k for the transistor bases and 10K for the pullup lines is a sensible minimum) and don’t leave any out! Also many PNP and NPN transistors should work - though I used a BC212L and BC182 respectively.


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